CN101034803A - Failure current limit method and device based on the rectifying bridge and bidirectional switch switching - Google Patents

Abstract

The invention discloses a fault limit flow method which is based on the rectification bridge and the double throw switch swithing, used bidirectional and unidirectional controllable electronic switching, composed a bridge path, in the electrical power system normal situation, controlled the bridge path work to no control rectification condition, once short-circuited fault occurrence, controlled the bridge path work immediately to two double throw switches conditions, would used for the current limiting super conductivity reactor or the conventional reactor string enters the exchange power supply system, limited the steady state value of the short-circuit current. At the same time, also discloses the fault current limiting equipment based on this method. This invention method and equipment apply to the alternating voltage power supply system, not only the initial period short-circuit current climbing rate of limiting short-circuit fault, also can limit short-circuit steady state value of occurring the short-circuit fault.

Description

Fault Current Limiting Method and Device Based on Rectifier Bridge and Bidirectional Switching

Technical field

The invention is a device applied to an AC voltage power supply system to limit the short-circuit fault current and its rising rate, and belongs to the technical field of AC flexible power transmission technology. Specifically, it is a short-circuit current limiting method and device based on a rectifier bridge and a bidirectional switch.

Background technique

With the continuous expansion of power system scale and capacity, the level of short-circuit current increases rapidly. When the level of short-circuit current exceeds the breaking capacity of circuit breakers, short-circuit faults may cause serious damage to major power equipment such as transformers, high-voltage switchgear, and power cables. damage, causing system instability, or even system paralysis. The short-circuit fault current limiter, after detecting the occurrence of a short-circuit fault, quickly changes the impedance parameters of the fault line to limit the short-circuit current to an allowable level to protect power equipment. It has become one of the key components of the flexible AC transmission system. Current limiters mainly include bridge solid-state current limiters based on power electronics technology and current limiters based on superconducting technology.

The dotted line in Figure 1 is the structure of the bridge-type superconducting current limiter proposed by the Westinghouse Electric Company of the United States. In the figure, L1 is a DC inductance, and Eb is a DC bias voltage, which is used to compensate the voltage drop of the diode to ensure that the current in the inductor L1 is always greater than the peak value of the load rated current, so as to ensure that the grid voltage has no distortion. Us is the power supply voltage, X1 is the line impedance, R1 is the load impedance, and CB is the circuit breaker. The superconducting current limiter has the following advantages: 1) it can quickly recover from a fault state; 2) the superconducting coil is direct current and has no alternating current loss; 3) it has no iron core, and the device has the advantages of light weight and low cost. However, the current limiter can only limit the current rising rate at the initial stage of the fault, but cannot limit the steady-state value of the short-circuit current, and the current limiting function is weak.

Contents of Invention

The purpose of the present invention is to overcome the defects in the prior art, and provide a fault current limiting method and device based on rectifier bridge and bidirectional switch switching, which can limit the short-circuit current rising rate at the initial stage of short-circuit fault, and can also limit short-circuit fault Steady-state value of short-circuit current after occurrence.

The present invention is a fault current limiting method based on a rectifier bridge and bidirectional switch switching, using bidirectional and unidirectional controllable electronic switches to form a bridge, and when the power system is normal, the bridge is controlled to work in an uncontrolled rectification state, Once a short-circuit fault occurs, the bridge is immediately controlled to work in two bidirectional switch states, and the superconducting reactor or conventional reactor used for current limiting is connected in series to the AC power supply system to limit the steady-state value of the short-circuit current.

The present invention is based on the fault current limiting device of the rectifier bridge and the bidirectional switchover, comprises the bridge circuit that is made up of electronic switch ES1, ES2, ES3 and ES4, DC current limiting reactor L1 and DC bias power supply Eb; Wherein, the electronic switch ES1 One end, one end of the electronic switch ES3 and one end of the DC current limiting reactor L1 are connected together; the other end of the DC current limiting reactor L1 is connected together with the negative pole of the DC bias power supply Eb; one end of the electronic switch ES2, the electronic switch ES4 One end and the positive pole of the DC bias power supply Eb are connected together. When in use, the current limiter is connected in series between the circuit breaker and the load of the power line; the other end of the electronic switch ES1, the other end of the electronic switch ES2 and the end of the line close to the power supply are connected together; the other end of the electronic switch ES3 , The other end of the electronic switch ES4 and the end of the line close to the load are connected together.

The electronic switches ES1, ES2, ES3 and ES4 are two-way controllable electronic switches, which is a realization scheme.

Taking electronic switches ES1, ES4 (or ES2, ES3) as two-way controllable electronic switches, and ES2, ES3 (ES1, ES4) as one-way controllable electronic switches is a realization scheme.

Reactor L1 can be superconducting or conventional, and superconducting reactors are more suitable for the method and device of the present invention.

The method and device of the invention are applied to an AC voltage power supply system, which can not only limit the rising rate of the short-circuit current at the initial stage of a short-circuit fault, but also limit the steady-state value of the short-circuit current after the short-circuit fault occurs.

Description of drawings

Fig. 1 is the circuit diagram of current limiting device of prior art;

Fig. 2 is the circuit schematic diagram of the fault current limiting device based on the rectifier bridge and the bidirectional switchover of the present invention;

Fig. 3 is the circuit diagram of the fault current limiting device based on the rectifier bridge and bidirectional switch switching of the present invention (bidirectional electronic switches ES1, ES2, ES3 and ES4 are all formed by two thyristor SCR antiparallel connections);

Fig. 4 is the circuit diagram of the fault current limiting device based on rectifier bridge and bidirectional switch switching of the present invention (electronic switches ES1, ES4 are bidirectional controllable electronic switches, ES2, ES3 are unidirectional controllable electronic switches);

Fig. 5 is the circuit diagram of the fault current limiting device based on rectifier bridge and bidirectional switch switching of the present invention (electronic switches ES1, ES4 are bidirectional controllable electronic switches, ES2, ES3 are unidirectional controllable electronic switches. Controllable bidirectional electronic switches have only one direction can be controlled, but the other direction is uncontrollable);

Fig. 6 is the circuit diagram of a kind of bidirectional switch when the present invention adopts self-turn-off device;

Fig. 7 is the circuit diagram of a kind of bidirectional switch when the present invention adopts self-turn-off device;

The circuit diagram of the one-way switch when Fig. 8 the present invention adopts self-turn-off device

Detailed ways

The present invention will be described in further detail below with reference to the accompanying drawings and examples.

Embodiment 1, as shown in Figure 3, the fault current limiting device based on the rectifier bridge and bidirectional switching, including a bridge composed of electronic switches ES1, ES2, ES3 and ES4, a DC current limiting reactor L1 and a DC bias power supply Eb; wherein, one end of the electronic switch ES1, one end of the electronic switch ES3 and one end of the DC current-limiting reactor L1 are connected together; the other end of the DC current-limiting reactor L1 is connected together with the negative pole of the DC bias power supply Eb; One end of the switch ES2, one end of the electronic switch ES4 and the positive pole of the DC bias power supply Eb are connected together.

The two-way electronic switches ES1, ES2, ES3 and ES4 are all composed of two thyristors SCR connected in antiparallel. When the system is normal, control thyristors T1, T2, T3, and T4 to be in the normally-on state, and control T5, T6, T7, and T8 to be in the off state, then the bridge composed of switching devices works in an uncontrolled rectification state. In the stable state after the inductor L1 is magnetized, since the bias power supply Eb compensates the on-state voltage drop of the switch tube, the slight current in L1 is greater than the peak value of the rated load current, and the current limiter is connected to the two terminals A and B of the line The voltage between them is zero, and the existence of the current limiter has no effect on the system. When a short-circuit fault occurs, the power supply voltage is added to the DC inductor L1 through the rectifier bridge, causing the current of L1 to increase. Since L1 is located on the DC side of the bridge, the voltage passing through the rectifier bridge has a single polarity. If the bridge has been working at In the rectification state, the L1 current will continue to increase. In this circuit, when the L1 current is greater than the set value, a trigger signal can be added to T1, T5, T4, T8 (or T2, T6, T3, T7) to ensure its conduction, remove T2, T6, T3, The trigger signal of T7 (or T1, T5, T4, T8) and ensure that these tubes are in the off state after the current crosses zero, that is, the control bridge is switched to a bidirectional switch state, and L1 is connected in series to the AC path, which can limit the The steady state value of the short circuit current. If it is ensured that when the positive half cycle of the power supply is short-circuited, turn on T1, T5, T4, T8 and turn off T2, T6, T3, T7; when the negative half cycle of the power supply is short-circuited, turn on T2, T6, T3, T7 and turn off T1, T5 . Compare).

Embodiment 2, as shown in FIG. 4 , is basically the same as Embodiment 1, except that the electronic switches ES1 and ES4 are bidirectional controllable electronic switches, and ES2 and ES3 are unidirectional controllable electronic switches. Under normal system conditions, the control switch tubes T1, T2, T3, and T4 are in the normally-on state, and T5, T6 are turned off. The bridge is in an uncontrolled rectification state. The function and characteristics of the current limiter in the circuit are the same as the above example. When a short-circuit fault occurs, the current in L1 rises rapidly. When it is detected that the current of L1 is greater than a certain set value, the control turns off T2 and T3 and turns on T1, T5, T4, and T6, then L1 is connected in series to the AC circuit, and L1 can limit the steady-state value of the short-circuit current in the AC circuit . This circuit has used two tubes less than the scheme shown in accompanying drawing 3. After a short circuit occurs in the negative half cycle of the power supply voltage, the L1 current will still bear the upper positive and lower negative voltages in the next half cycle, so the L1 current may start from the peak value of the load current rating and continue to increase within one cycle, so the L1 current , the rated current value of inductance and switching tube will be bigger than the scheme shown in accompanying drawing 3.

Embodiment 3, as shown in FIG. 5 , is basically the same as Embodiment 2, except that in this solution, the controllable bidirectional electronic switch can only be controlled in one direction, and the other direction cannot be controlled. Under normal circumstances, control T2 and T3 to turn on, and T1 and T4 to turn off, then D1, D2, T2 and T3 form an uncontrolled rectifier bridge. After the short-circuit fault occurs, turn off the T2 and T3 tubes, control the T1 and T4 tubes to be in the normally-on state, and then the inductor L1 is connected in series with the AC circuit to limit the steady-state value of the short-circuit current. The parameter calculation of this circuit is the same as that shown in Figure 4, but it is simpler and the cost is lower.

In the above solution, the controllable electronic switch adopts a silicon controlled rectifier or a combination of a silicon controlled rectifier and a diode, or a self-turn-off device, such as IGBT, IGCT, GTO, etc. can also be used. When tubes such as IGBTs are used, because they are equivalent to being used in current source circuits, the bidirectional switch can adopt the connection method shown in accompanying drawing 6 and accompanying drawing 7, and the unidirectional switch can adopt the method shown in accompanying drawing 8. The topological structure of the main circuit after adopting the self-shutdown device is modeled on the accompanying drawings 3, 4 and 5.

Claims (7)

1, a kind of failure current limit method based on rectifier bridge and bidirectional switch switching, the steps include: to adopt two-way and unidirectional controllable electronic switch, form a bridge circuit, under the normal situation of electric power system, the control bridge circuit works in does not control rectification state, in case short trouble takes place, controls bridge circuit immediately and works in two bidirectional switch states, the superconduction reactor or the conventional reactor that will be used for current limliting seal in ac power supply system, with the steady-state value of limiting short-circuit current.

2, a kind of Fault Current Limiting Device based on rectifier bridge and bidirectional switch switching comprises the bridge circuit, direct current current-limiting reactor L1 and the dc bias power Eb that are made up of electronic switch ES1, ES2, ES3 and ES4; It is characterized in that: one of the end of electronic switch ES1, the end of electronic switch ES3 and direct current current-limiting reactor L1 terminates at together; The other end of direct current current-limiting reactor L1 and the negative pole of dc bias power Eb are connected together; The positive pole of the end of electronic switch ES2, the end of electronic switch ES4 and dc bias power Eb is connected together.

3, the Fault Current Limiting Device based on rectifier bridge and bidirectional switch switching according to claim 2, it is characterized in that: described electronic switch ES1, ES2, ES3, ES4 are two-way controllable electronic switch.

4, the Fault Current Limiting Device based on rectifier bridge and bidirectional switch switching according to claim 2, it is characterized in that: described electronic switch ES1, ES4 or ES2, ES3 are two-way controllable electronic switch, ES2, ES3 or ES1, ES4 are unidirectional controllable electronic switch.

5, according to claim 2,3 or 4 described Fault Current Limiting Device based on rectifier bridge and bidirectional switch switching, it is characterized in that: described controllable electronic switch adopts half control device controllable silicon.

6, according to claim 2,3 or 4 described Fault Current Limiting Device based on rectifier bridge and bidirectional switch switching, it is characterized in that: described controllable electronic switch adopts self-turn-off device.

7, according to claim 2, the 3 or 4 described Fault Current Limiting Device of switching based on rectifier bridge and bidirectional switch, it is characterized in that: what described reactor L1 can be for superconduct, also can be for conventional type.

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